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E is for Emerald

Updated: Dec 5, 2021

In our next instalment of A-Z Gemstones Uncovered, we’ll be taking a look at the lushest of the lush, or what Pliny the Elder quoted in his book, Natural History, published in the first century AD: “…nothing greens greener” - Emeralds!

So as always let's begin by looking at where it all started…

The first known Emerald mines on record were found in Egypt as early as 330 BCE but some people estimate that the oldest Emeralds could be 2.97 billion years old.

Around 323 BCE, during the time of Alexander the Great, Ancient Greek miners came across and discovered the mines which would come to produce the Emeralds favoured and adored by Cleopatra. During this time, the majority of Emeralds came from Egypt. Once Cleopatra’s reign began (51 BCE - 21 BCE) mining became even more popular as demand grew. The mines we now refer to as “Cleopatra’s mines” or “Mons Smaradgus” (Emerald Mountains) were thought to be a myth as no records of their existence remained after being abandoned in the early Middle Ages (500 to 1500 CE). However, the remains of these mines and the extensive work that was carried out were rediscovered by French explorer and mineralogist, Frédéric Cailliaud, who found them just as they’d been left more than five hundred years ago.

During the 16th century, the Spanish invaded the New World, otherwise known as South America. The Incas had been using Emeralds in their jewellery and religious ceremonies for at least 500 years and were prized possessions. The Muzo Indians of pre-Colombia had well-hidden and treasured Emerald mines which took the Spanish invaders almost 20 years to find. Once found, the Spanish traded Emeralds for precious metals as they treasured gold and silver far more than gemstones. These trades opened the eyes of European and Asian royalty who fell in love with the green jewels causing Emeralds popularity to soar.

So let us dive into the science of how these little green beauties are formed…

Emeralds are a type of mineral known as Beryl. When Beryl is pure it is colourless, therefore trace elements or chemical impurities cause the appearance of colours during the formation period. Emeralds are not only created this way but also stones such as Aquamarine and Morganite.

Emeralds tend to form in metamorphic rocks, volcanic deposits or cracks in granite rocks. Within these areas are hydrothermal veins, these are created when hydrothermal (hot water) fluids have escaped from the magma deep in the Earth’s crust. The formation of Emeralds begin to form when fluids containing certain elements such as beryllium and cool down within the veins. If there is enough space, beryllium, aluminium, silicon and oxygen all come together (under the right temperature and pressures) causing the formation of hexagonal crystals known as Beryl. When the elements, chromium or vanadium are present, the Beryl absorbs these “impurities” and turns vivid green, forming what we refer to as Emeralds. Stones that have not saturated enough of these impurities and are not “green enough” are called “Green Beryl” instead. Emeralds can also form in pegmatite deposits, where magma, instead of hydrothermal fluids, cool. This process happens over an extremely long time, natural Emeralds today formed hundreds of million years ago.

Emeralds are one of four precious gemstones known globally around the world (diamonds, sapphires and rubies are the other three). However, they are classed as “Type III” gemstones as they almost always contain flaws. These flaws or inclusions are to be expected in Emeralds, they are found in 99% of them, therefore if you find a "flawless" stone it is most likely synthetic. These inclusions actually increase the value of the stone due to their attractive patterns and uniqueness.

Emeralds measure 7.5-8 on the Mohs Scale of Hardness. The scale runs from 0 (softest) to 10 (hardest). As a comparison glass measures 5. Despite Emeralds hardness, the inclusions create a natural weakness in the stone, making them prone to chipping or shattering if too much pressure is applied. They are known to spontaneously disintegrate during the lapidary process causing a lot of waste.

Where are Emeralds found?

Emeralds are found all over the world in countries such as Austria, Bulgaria, Cambodia, France, Germany, India, Italy, Mozambique, Namibia, Norway, Russia, South Africa and the United States (mostly in Connecticut, Montana, Nevada, North Carolina and South Carolina). However today they are mostly found and mined in Colombia, Brazil and Zambia.

Colombia is the world’s largest producer of Emeralds, contributing to more than 50% of worldwide production. The main Emerald mines are in Muzo, Coscuez and Chivor. Rare “trapiche” Emeralds are also found in Colombia, these are distinguished by inclusions mimicking a radiating star from the centre of the stone caused by dark impurities.